Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W=map(int,input().split())
S = [list(input()) for _ in range(H)]

white = 0
for i in range(H):
  white += S[i].count('.')

q = [(0,0)]
S[0][0] = 0
while q:
  qq = []
  
  for xy in q:
    x,y = xy
    for dx,dy in ((1,0),(-1,0),(0,1),(0,-1)):
      if not(0 <= x+dx < W) or not(0 <= y+dy < H):
        continue
      elif S[y+dy][x+dx] != '.':
        continue
      S[y+dy][x+dx] = S[y][x] + 1
      qq.append((x+dx,y+dy))
  if S[-1][-1]!=".":
      break    
  q = qq

print(white - S[-1][-1] -1 if S[-1][-1] != '.' else -1)